• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.1
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• pp.63-69
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• 2006

New design equations for calculating the lateral-torsional buckling moment resistances of singly stepped I-section beams subjected to general loading on the top flange are suggested based on the investigations of elastic finite-element analyses. The new equations presented in this study are compared with current moment gradient modifiers presented by other researchers and specifications. The study considered almost loading cases on buildings and bridges. The proposed equations should be easily used to calculate the lateral-torsional buckling moment resistance of stepped I-beams.

• Journal of the Korean Data and Information Science Society
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• v.28 no.1
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• pp.87-98
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• 2017

The multivaiate empirical distribution function (MEDF) is defined in this work. The MEDF's expectation and variance are derived and we have shown the MEDF converges to its real distribution function. Based on random samples from bivariate standard normal distribution with various correlation coefficients, we also obtain MEDFs and propose two kinds of graphical methods to visualize MEDFs on two dimensional plane. One is represented with at most n stairs with similar arguments as the step function, and the other is described with at most n curves which look like bivariate quantile vector. Even though these two descriptive methods could be expressed with three dimensional space, two dimensional representation is obtained with ease and it is enough to explain characteristics of bivariate distribution functions. Hence, it is possible to visualize trivariate empirical distribution functions with three dimensional quantile vectors. With bivariate and four variate illustrative examples, the proposed MEDFs descriptive plots are obtained and explored.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.49-60
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• 2005

This paper presents the results of an investigation on the effects of design variables on the behavior of geosynthetic-reinforced modular block walls in a tiered arrangement using the finite-element method of numerical analysis. A parametric study was performed by varying the offset distance between the tiers and reinforcement length of the lower and upper tier using verified finite-element model. The finite-element analysis provided relevant information on the mechanical behavior of the tier wall and interaction mechanism between the upper and lower tier, which was otherwise difficult to obtain from the limit-equilibrium analysis based current design approaches. Practical implications of the findings obtained from this study in the current design approaches are discussed in great detail.

• Journal of the Society of Disaster Information
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• v.8 no.2
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• pp.148-157
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• 2012

Recently, evacuation safety of building residents becomes the major concern, as the building has been higher and more complicated. Many high-rise multi use buildings are under construction in Korea. Required evacuation time using stairway is longer in high-rise buildings, moreover it is impossible for the disabled to evacuate by using stairway. For this reason the study on the effectiveness of using elevator for evacuation is being progressed. Elevator shaft flow coefficient is the major factor for the calculation of elevator piston effect. The results of this study can be used for the study of elevator piston effect as basic data. The flow coefficient simulation was performed using FLUENT, commercial CFD program. As a result of the flow coefficient simulation, the coefficient is 0.88 considering the safety factor. This result is verified that the result of experimental study, 0.86 is conservative.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.245-245
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• 2010

우리나라 생활폐기물 중 음식물쓰레기는 가장 많은 부분을 차지하고 있다. 또한, 음식물쓰레기에서 발생되는 음폐수의 발생량은 8,926톤/일에 달하고 있지만, 이 중 극히 일부만이 하수처리장 등에서 병합 처리되고 있고 대부분은 해양 투기되고 있는 실정이다. 이에 본 연구에서는 독일 GBU사로부터 중온/습식/이상 혐기성 소화 기술을 도입하여 HADS Pilot Plant를 설치하였고, 2008년 3월부터 국내 음폐수 및 음식물쓰레기에 적합한 최적의 운전기술을 확보하기 위한 Pilot Test를 실시하였다. 본 실험에 사용된 HADS Pilot Plant는 산발효조($6m^3$), 메탄발효조($50m^3$), 안정화조/가스저장조($40m^3$)그리고 가스 소각기로 구성되어 있다. 그리고 적용 음폐수 및 음식물쓰레기는 경기도 Y군에 위치한 사료화 시설에 반입되는 것을 이용하였는데 음폐수는 평균 TS 13.5%, VS 80%, pH $3.7{\pm}0.2$의 성상을 나타내었다. 이를 이용해 계단식으로 유기물 부하를 증가시키면서 $4kgVS/m^3/d$까지 적용하며 중온 상태에서 혐기성 소화를 실시한 결과, $0.8Nm^3/kgVS_{rem}/d$의 바이오가스 회수 및 85%의 VS 감량이 가능함을 확인하였다. 그리고 음식물쓰레기는 음폐수와 달리 1차 파쇄/선별기 및 배관상에 설치되는 2차 미세파쇄/선별기를 통한 전처리를 실시하였고, 1차 파쇄/선별 후 평균적으로 TS가 17.4%, VS는 81%, pH는 $3.85{\pm}0.2$의 성상을 나타내는 음식물쓰레기를 2차 미세파쇄/선별기를 거쳐 Pilot Plant의 산발효조에 투입하여 중온상태에서 혐기성 소화를 실시하였다. 음폐수 적용시와 마찬가지로 계단식으로 유기물 부하를 증량하면서 $4kgVS/m^3/d$까지 적용하여 운전하였고, 그 결과 약 $0.9{\sim}1.2Nm^3/kgVS_{rem}/d$의 바이오가스 회수와 85~87%의 VS 감량 효율을 확인하였다. 음폐수와 음식물쓰레기의 혐기성 소화 실험 결과, 제거된 VS량을 기준으로 보았을 때, 음식물쓰레기에서 더 많은 바이오가스 발생하였는데 이는 음식물쓰레기에 존재하는 고형물이 미생물들의 서식 공간으로 활용됨에 따라 혐기성 소화 과정에서 일어나는 혼합 발효 및 공영양 대사가 음폐수 대비 좀 더 수월하게 일어날 수 있게 된 데에 따른 결과라고 생각된다. 당사의 HADS Pilot Plant test에서는 계단식의 순차적인 유기물 부하 증량과 총VFA/총 알카리도 비율을 0.3~0.4 수준이하로 유지하며 운전함에 따라 음폐수와 음식물 모두에서 안정적으로 $4kgVS/m^3/d$까지의 유기물 부하 적용이 가능하였다. 또한, 생산된 바이오가스 내 메탄의 함량은 60~65%를 유지하였으며, 메탄발효조의 pH는 별도의 조절이 없이도 운전기간 동안 평균 7.8~7.9 수준을 유지하였다. 이처럼 pH 3.7~3.8의 음폐수 또는 음식물쓰레기의 투입에도 안정적인 완충능력을 보여준 것은 소화조 내에서 기질로부터 분해되어져 나오는 암모니아와 이산화탄소가 강력한 버퍼 시스템을 구축하고 있음에 따른 결과로 사료된다. 그리고 음폐수와 음식물쓰레기의 경우 모두 85%이상의 높은 VS 제거율을 보여주었는데 이는 당사의 HADS Pilot Plant 소화조의 구조가 내통과 외통으로 구분되어져 있음에 따라 plug flow + CSTR의 특징을 가짐에 따른 결과로 판단된다. 상기한 결과를 바탕으로 향후에는 $5kgVS/m^3/d$ 수준의 유기물 부하 적용운전도 계획하고 있다.

• Current Research on Agriculture and Life Sciences
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• v.14
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• pp.85-100
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• 1996

The Studies were conducted to provide the state of mulberry cultivation and it's development in Banguet province (high land) of Philippines. Philippines initiated the sericulture industry with the technical asistance of Japan in 1974 and established mulberry field and sericultural facilities with technical asistance of Korea in 1990 and 1995. The required average of 100 to 150mm per month is not available during the dry season from December to March. Therefore mulching with grass which is available abundantly in the Philippines should be established to conserve moisture, to control soil erosion, surface ran-off and also to increase the humus content in the soil. In chemical properties of mulberry field, the pH value of soil is 4.7, organic matter 1.6%, and available phosphorus 6ppm. Therefore, all fields should do liming and be applied compost. To improve leaf yield for mulberry planted under partial shade area of pine trees, more pruning of pine tree should be done for good sunshining of mulberry, more liming and compost should be applied to improve acidic soil. To control the leaf roller, DDVP and KAFIL are able to be used. When spraying insecticides to control mulberry insect pests, care should be taken to consider the residual effects of chemicals on the leaf. Leaf should be fed to silkworms only after the leaves are free of any residual effects.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.72-79
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• 1998

Static deformation theory of elastoplastic structures can be applied only if the magnitude of loading is less than the plastic collapse force $F_c$. However, with impact or explosive blast loading, the structure can be subjected to an intense but short-duration force pulse that exceeds the plastic collapse force and initiates structural collapse. In this paper, the dynamic response of a rigid-perfectly plastic cantilever subject to intense impact loading is examined in terms of the plastic collapse force. When a step loading is applied, the motion of the beam is calculated and analyzed through the non-dimensionalization of variables. It is concluded that the motion of a beam can be characterized as a function of the nondimensionalized force parameter, $f{\equiv}F/F_c$, where $F_c$ represents the critical force for plastic collapse. This result is used to the analysis of the beam motion subject to rectangular force pulse.

• Journal of Korean Society of Steel Construction
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• v.18 no.2
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• pp.191-201
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• 2006

New design equations for calculating the lateral-torsional buck ling moment resistances of stepped I-section beams with/without continuous lateral top-flange bracing subjected to a point load, a series of point loads, and a uniformly distributed load, are suggested based on the results of elastic finite-element analyses. The new equations presented in this study are compared with the current moment gradient modifiers presented by other researchers and specifications. Although the study paper presents mainly stepped-beam cases subjected to a point load and a uniformly distributed load. The proposed equations include the length-to-height ratio effects for stepped beams with continuous lateral top-flange bracing. The new moment gradient correction factors could be easily used to calculate the lateral-torsional buckling moment resistance of stepped I-beams.

• Journal of Life Science
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• v.18 no.11
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• pp.1532-1537
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• 2008

The purpose of this study was to investigate the effect of different arthroplasty designs on knee kinematic and lower limb muscular activation for up-stair and down-stair movement. 3-D video analysis of whole body and joint kinematics and EMG analysis of quadriceps and hamstrings were conducted. One-way ANOVAs were used for statistical analyses (p=0.05). The single-radius group exhibited more arthroplasty limb quadriceps EMG and hamstring coactivation EMG than the multi-radius group. Single-radius demonstrated more abduction angular displacement and reached peak abduction earlier than the multi-radius arthroplasty limb. The single- radius the percent body fat showed similar values in the Elderly, Single and Multi-radius group among the periods, however Control group was Lowered among the periods. Single-radius group limb also increased the quadriceps muscle activation level to produce more knee extension moment to compensate for the short quadriceps moment arm. Resting metabolic rate was significantly increased in control group in the period of LI. Energy expenditure was extremely increased in all groups except control group among the periods. We can say this is the exercise effects.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.185-186
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• 2011

본 논문에서는 최근 직류송전용 컨버터로 많은 관심이 집중되고 있는 모듈형 멀티레벨 컨버터(Modular Multi-level Converter)에서 출력파형의 고조파를 저감하는 모듈레이션 방법과 각 모듈의 직류전압 불평형을 해소하는 알고리즘에 대해 기술하고 있다. 먼저 본 논문에서 임의의 개수로 반브리지 모듈이 주어졌을 때 고조파 레벨이 최소화되도록 다펄스 형태로 출력파형을 형성하는 방식을 제안하고 그 타당성을 PSCAD 소프트웨어를 이용한 시뮬레이션으로 검증하였다. 이 방식은 다펄스 출력파형의 각 계단을 형성하는 모듈의 턴온과 턴오프 시점을 보편화된 수식으로 정하는 방식으로 알고리즘 구현이 매우 용이하다. 또한 각 모듈의 직류전압 불평형을 바로잡는 알고리즘을 제안하고 그 타당성도 시뮬레이션으로 검증하였는데, 이 방식은 각 모듈이 교류 매 반주기마다 생성하는 펄스의 크기를 순차적으로 형성하는 것으로 알고리즘의 구현이 용이하다. 본 논문에서 제안하는 알고리즘은 향후 국내에서 모듈형 멀티레벨 컨버터를 개발할 때 유용하게 활용될 것으로 보인다.